Celestial navigation instrument



June 26, 1945. F. CHAMBERLAIN 2,378,931

CELESTIAL NAVIGATION INSTRUMENT Filed Sept. 3, 1943 10 Sheets-Sheet 1 Fig.1

IN VEN TOR.

June 1945- F. CHAMBERLAIN 73 CELESTIAL NAVIGATION INSTRUMENT Filed Sept. 3, 1943 10 Sheets-Sheet 2 Fig.3

L--H6 I 51 l A7 M4 H8 E E. 610 IE INVENTOR.

June 26, 1945. F. CHAMBERLAIN 2,378,981

CELESTIAL NAVIGATION INSTRUMENT K30 K64- F41 K1 J 1 B? K 7% M 2 7 0 61- '1 M3 A5 A1 "4:

l I N A6 C1 A40 F1 1 VEN TOR June 9 F. CHAMBERLAIN GELESTIAL NAVIGATION INSTRUMENT Filed Sept. 5, 1943 10 Sheets-Sheet 4 IN VEN TOR.

June 26, I945. F. CHAMBERLAIN 2,378,981

CELESTIAL NAVIGATION INSTRUMENT Filed Sept. 3, 1943 10 Sheets-Sheet 6 Z15 A6 L15 ms 015 16 19 a0 v I I a T2914 24 Z14 o T14 914 H Fig.1.;

June 26, 1945. F. CHAMBERLAIN 2,378,931

CELESTIAL NAVIGATION INSTRUMENT Filed Sept. 3, 1945 10 Sheets-Sheet 9 W\ W\ 26 H.

Patented June 26, 1945 CELESTIAL NAVIGATION DISTRUMENT Francis Chamberlain, Arlington, Mass.

Application September 3, 1943, Serial No. 501,123

22 Claims.

This invention relates to a celestial navigation instrument and method for solving the problems of navigators astronomical triangles. its principal use is in the solution of usual Summer lines of position, and obtaining azimuth and intercept, although it is also of use in determining the identity, the time of rising or setting of a celestial body, and the time at which such a body will be on the prime vertical. The invention also may be employed in determining initial course and great circle distance between any two points on the earths' surface that lie on the same side of both branches of a meridian and are not over 90 apart. Any and all of such. problems may be readily solved by. this invention without employing bulb and troublesome tables such, for example, as H. O. 214.

A great advantage of the apparatus is that it may be made to record visibly on counters the given data and the determined data in connection with the various uses of the instrument. The instrument is particularly valuable in airplanes where navigators must perform their duties under conditions of fatigue, unsteadiness, reduced oxygen, cramped quarters and inadequate light-all of which handicaps are substantially avoided by the present invention together with errors that would otherwise result therefrom.

In the drawings- Figs. 1, 2 and 3 are diagrams illustrating the method, or mode of operation, employed in the use of th instrument;

- Pig. 4 is a plan view of the instrument;

.Fig. 5 is a vertical cross-section on the line I-Iof Fig. 4;

Fig.6 is a plan on the line 5-6 of Fig. 5;

Fig. "I is a plan on the line 1-1 of Fig. 5 showing the bars M and P; s

Fig. Bis-an elevation, partly in section, from the left of Fig. 7;

the observed image as seen through the eye tube;

Fig. 13 is a top plan view of the vices;

Fig. 14 is a plan view on the line l4-l4 of Fig. 15;

45 of the earth, and the horizontal diameter Q, Ql

Fig. 15 is an elevation on the line 15-15 of Fig. 14; Fig. 16 is an elevation on the line iG-lii of Fig. 14;

counter de- V Fig; 17 is an elevation on the line il-il of Fig. 14;

- Fig. 18 is a perspective view of the clutch operating devices shown in Fig. 1'7;

Fig. 19 is an elevation on the line' l9-l9 of Fig. 14; v

Fig. 20 is an elevation on the line. 20-20 of Fig. 14;

Fig. 21 is an elevation on the line 21-21 of -Fig. 14; 15.

Fig. 22 is a. vertical cross-section of the Y knob;

Fig. 23 is a plan view on the line 23-23 of Fig. 22;

Fig. 24 is a plan view on the line 24-24 of Fig. 15;

Fig. 25 is a plan view on the line 25-25 of Fig. 15;

Fig. 26 is an elevation on the lin 26-26 of Fig. 25;

Fig. 27 illustrates means to operate the instrument without the counter mechanism;

Figs. 28-32 illustrate a modification of the counters so as directly to obtain and indicate the intercept, in which Fig. 28 is a fragmentary plan view illustrating the intercept counter;

Fig. 29 a view illustrating the mechanism of the device of Fig 28;

Fig. 30 an elevation of 28 and 29, and

Figs. 31 and -32 are views illustrating the counters of Fig. 28. Figs.. 1, 2 and 3 diagrammatically illustrate the procedure for ascertaining the altitude h and the azimuth 2 01a celestial body when the assumed or D. R. (dead reckoning) latitude l of the observer and the declination d and the local hour angle 15 of the body are given. A is a circle representing the meridian oi the observer in a plane representing the observers meridian plane. The center of A is at ll, representing the center represents the line produced by the intersection Diane.

representing the projection on the observers meridian plane of the ground point of the celestial body, 1. e., the point G is the intersection with the observers meridian plane or a line perpendicular to said plane and passing the apparatus of Figs.-

The first procedure is to locate the point G through the ground point on the surface of the earth.

- The procedure is as follows:

A diameter D, 0, DI is drawn to make an angle Ql, 0, DI, equal to'the' declination d, with the line Q, Ql. Then ll, B2l equals cos d.

A horizontal line M2, parallel to Q, Ql, is drawn through DI, i. e., at a distance sin d from Q, Q

A radius OT is drawn making an angle Q, 0, T, equal to the local hour angle t, i. e., t=Q, 0, T. A point B22 on line 0, T is noted at a distance from equal to cos d.

The intersection g of the perpendicular P3 through B22 and the diameter Q, Qi is at a distance from 0 equal to cos d cos i. The intersection G of perpendicular P3 with line M2 is the projection of the ground point of the celestial body on the observer's meridian plane.

The next procedure is to measure the altitude h of the celestial body, assuming that d and l are of the same name (either both north, or both south), as follows:

A radius is drawn making an angle with the line 0G- equal to the co-latitude (90-l) of the observer and on that line a point E is located at a distance from 0 equal to ll, G. The diameter Q, Q! in relation to point E now represents the line of intersection of the observers horizon plane with his meridian plane.

This same point E' is located in Fig. 2.

A horizontal line M5, drawn through E, Fig. 2, intersects the circle A at H. The angle Qi, B, H equals the altitude h of the celestial body, i. e, h:Q|, 0, H.

The next procedure is to measure the azimuth z of the celestial body.

A line PB, through the point E perpendicular to Q, Ql, intersects a circle having a radius equal to cos it at IBM. The angle Qt, l], B24 equals the azimuth 2, measured from the elevated pole.

To sum up:

ltzGi, t, H and e=f9l, ll, .BlM

If at and Z are of opposite names (one north or south and the other south or north), the same procedure is followed to locate the point t3 the projection of the ground point of the celestial body.

The point El, Fig. 3, is located on a radius making an angle 9U+l with 0, G, and at a distance 0, G from 0.

Proceeding as before to locate the points H2, and B25, and B26, the'altitude h andthe azimuth 2 measured from the elevated pole respectively of the celestial body are- I h=QI, ll, H2 and e=Q, 0, B26

The angle 90-Z or 90+l is the angle made by the plane of the observers horizon with the plane of the equator. If the declination is the same name (north or south) as the latitude, the angle is 90l. If the declination is of the opposite name to the latitude, the angle is 90+Z.

As provided in the modification of Figs. 28-32, hereinafter explained, the intercept may be directly obtained and indicated by counters in place of the computed latitude without any calculation by the operator.

In the following description the expressions up and down and right and left or similar expressions are used, where the context is appropriate, with reference to the figures as drawn on the sheets. In practice the instrument is held in a horizontal position with the crank All, Fig. 13, on the right, convenient to the operators righthand, and the figures on the counters are right side up and when read from the left.

The moving parts of the apparatus are mounted upon a frame F, at the center 0 of which is a stud Fl, Figs. 4 and 5. The stud has a head Fl I, Fig. 5, which is pulled down by a bolt FI2 and washer F13 against a ball bearing to press and center the hub C0 of the quadrant C against the balls in the annular groove in the wheel A. The wheel A bears on and is centered by the balls in the annular groove in the frame F. By these means the wheel A and the quadrant C may turn with the minimum of friction about the center 0.

The wheel A has on its circumference three hundred and sixty worm teeth Al, one tooth being equal to one degree. Meshing with these worm teeth is a worm wheel A5 fixed on a shaft A5 in bearings Al, Fig. 6. Shaft A6 extends into the box containing the counter mechanism, Figs. 13, 14 and 15. One revolution of the shaft Al moves the wheel A- one tooth or one degree.

Shaft A6, Figs. 16 and 17, has fixed thereon a gear A64 which meshes with gear Ll5. Gear L15 is one of a, train of meshing gears, Li5, Tl5,

D15 and Hi5, Fig. 14. Gear A64 also meshes with gear Zi5, Fig. 16. These gears may be loose on the shafts LM, TM, D, H and Zll, respectively, or preferably, to minimize friction, they may be mounted on ball bearings on hubs fastened to and projecting from. the side of the frame. Gear HI ii meshes with gear A6 I which is operated by the crank All, Fig. 142. Rotating crank All rotates all the genre, the shaft A8 and the wheel A.

Means are provided to lock the wheel A in its zero position, Fig. 6'. A collar A20, fast on shaft A'li, has a recess A2! into which a pin A22 may project when the wheel A in zero position. Then a pin A23 thereon strikes the arm A25 of a three arm lever AN and, against the tension of spring All, lifts its arm A28 above, or below, a pin AM on one end of lever Adi pivoted at A32 to the frame, thereby permitting the spring A33 to pull the upper end of lever AM to the left and project the pin A22 into the recess A2 I. The pin A22 has a pin and slot connection with the upper arm of lever AM. To withdraw the pin A22 and thereby release the shaft A5 and the wheel A, the rod A35 is lifted, thereby rocking lever All to pull the link A31 and the upper end of lever Ail to the right. Then, when the wheel A is turned clockwise or anticlockwise, as it is in the operation of the instrument, the pin A23 releases the arm A25 of lever A25 and the spring A21 rocks the lever to bring its left end A28 into register with pin A30 and, provided rod A35 is lowered, to hold the lever A3l and the pin A22 in retracted unlocking position.

On the right-hand side of wheel A is a vertical pin A9, Figs. 4, 5 and 6, the center of which lies on the horizontal line through the center 0 of the wheel A. Pin A9 controls the movement of straight-edge means, as here shown a horizontal bar M, Fig. '7, which is pressed upward against the pin and has an engraved line M0 above and passing through the extended axis of the pin. This line I call the indicative line of bar M.

The bar M has at its right end a block Mi provided with rollers M2 which'slide in guides M3 and maintain the'bar horizontal. The bar M is pulled upward and held against the pin A! by a cord MIS wound on a reel MIG on a shaft M". The shaft is turned so as to wind the cord onto the reel by a coiled spring (not shown) in the box MN. I

When the wheel A is turned clockwise about 0. the pin A9 pushes the bar M, against the tension of the spring, downward to a position depending upon the degree of rotation of the wheel A. The bar M may then be clamped in position b a rod M4, Fig. 8, which is pivoted at M5 on the frame and extends parallel to the guides M3 and lies above a friction pad Ml in the block Ml. A spring M6 presses rod M4 down to bear against the friction pad. The rod -M4 has a beveled end. Fig. 26, by which it may be lifted by a rod M40 which has a beveled end adapted to pass under the beveled end of rod M4. When the rod M40 is moved down, Fig. 25, it releases rod M4 so that t e spring M6, Fig. 8. presses the rod M4 against the friction pad M1 in the block MI and thereby clamps the bar M to the frame.

A quadrant C. mounted on ball bearin s centrally of the frame. Fi 6, is provided with internal gear teeth Cl. the pitch line of which is spaced from the center a distance equal to the distance of the center of the pin A9 from the center 0. A spring C2, Fig. 5, urges this quadrant clockwi e relative to wheel A and its movement n that direction is limited by a stud on the quadrantscontacting with a stop F3 on the frame. Fig.

The quadrant C is clutched to the wheel A when it is desired to move them together. Pivoted at C3, Fig. 6, to the quadrant C is a clamping lever C4 having a friction pad C5. These parts project down into and lie in a groove Al2 in the wheel A. The other end of the lever C4 has a vertical pin C6 which projects upward through a slot C31 in the plate C30 fastened to quadrant C. A spring C8! pulls on pin C6 to withdraw the clamping lever and friction C from the side of the groove A|2 in wheel A. To set the clamp, a cam C8, pivoted at C9 in the plate C30. is pressed against the pin C0 by the rocking of a lever CIO pivoted at Cl l on the frame F. The lever CHI is rocked by the rising of a. rod CIZ, which has at its upper end a pin C|3 which raises the right end of lever CM and depresses its left end to set the clamp. The hub of thecam C8 is provided with ratchet teeth C20 which are engaged by a pawl C2! pivoted to plate C30 and pressed into engagement with the teetlr by a spring C22. The pawl locks the cam C8 in clamping position, so that the rod Cl2 and the lever Cl0 may be returned to neutral position without releasing the clamp.

To release the pawl C2! and thereby the cam C8 and the clamp, the rod OH is depressed thereby moving down the pin C13 to depress the end of lever Cl'l pivoted at CIB to the frame. The lever CH depresses the tail of the pawl C2! to rock the pawl and disengage it from the teeth C20 on the hub of the cam C8. The spring C8! then pulls the pin C0 to lift the lever C4 and the friction pad C5 out of contact with the side of the groove Al2 in the wheel A.

.A segment B, Fig. 6, i pivoted on a pin A40 on the wheel A, the center of this pin being at a distance from 0 equal to one-half of the distance from 0 to the pitch lineof the ear teeth CI. Th quadrant C has an arcuate slot C40 through which the pin A40 projects so that the pin may move relative to the quadrant as is necessary in the operation of the instrument.

The segment B has gear teeth Bl on its periphery which mesh with the internal gear teeth CI of the quadrant C. On the left end of the segment B is a pin B2, the axis of which, when th parts are in their zero position, is over the common pitch line of the meshing gear teeth BI and Cl and on a line through the centers A9, 0 and A extended. This pin 132 controls the movement across the instrument of a second straight-edge means, as here shown a bar P. As an alternative or equivalent construction for the two straight-edge means shown in the drawings, M and P, or either of them, any other means for suitably delineating intersecting lines may be employed, for example, suitably mounted tightly stretched wires, transparent members carrying an indicative line, or optical means such as lightprojecting devices whereby a straight indicative line is provided. v

The bar P, Fig. '7, has at its lower end a block Pl provided with rollers Pl l'to slide transversely in guides PIZ on the frame. The bar has a slot P2, Fig. 9, in its bottom surface into which the pin B2 on the segment B projects, so that the turning of th segment B about the pin A40 moves the bar P bodily transversely.

The bar P has a part Pl3 fixed thereon on blocks, thereby providin a slot between the parts, in whichthe bar M may reciprocate.

On P13 is an engraved linePl above and parallel t0 the slot P2, Fig. 7. This line P4 is offset from a line which is parallel to the length of the bar and passes through the extended axis of the pin B2. I call this line the indicative line of bar P. The engraved line P4 is offset to the left from the indicative line by such a distance that when the line P4 is seen through the eye tube R, as will be described, as tangent to the reticle RI I, Fig. 12, the indicative line (shown in dot and dash) passes through the center of the reticle. As the reticle is a circle the offset distance of the line P4 from the indicative line is equal to the radius to the outer circumference of the reticle.

A slave ring J, Fig. 5, concentric with 0, is mounted on ball hearings on the frame F. This ring is rigidly connected by a post J l to the wheel A and is in effect a part of wheel A.

The ring J may be marked, Fig. 4, with a. circular scale divided into 180 degrees for each semicircumference, so that a pointer S, fast on the frame, indicates the number of degrees by which the wheel A is turned clockwise or anticlockwise from the zero mark to which the pointer points when the wheel A is in its zero position.

A ring K, Figs. 4 and 5, concentric with 0, is mounted on ball hearings on the ring J. It is provided with parallel parts Ki and K2 on which an eye tube device, to be described, is mounted so as to be slidable radially.

A clamp is provided to clamp the ring K to the frame and another clamp to clamp the ring K'to the ring J.

To clamp the ring K to the top plate F of the frame, two triangular clamp plates K40 and K, Fig. 4, are pivoted to the ring K. To each of these plates is pivoted a link K42, which is pivoted to the end of a cross bar K43. The cross bar is urbed upward to release the clamp plates by aspring K embracing va pin whichholds the spring between the cross bar and block-K46 fixed on a part K41 of ring K. A cam K is fixed on a pin K5! journaled in the prongs of a clevis K49 slidable. on the upper surface of K41. The cam K" may be turned by the handle K52 to depress the cross bar Kl: to press the clamp pieces KAI andl Kll against the frame. Also, the turning of the cam Kin moves the clevis K" and the pin K to press the pin against the frame plate FlI. Thus the movement of the handle K52 in one direction clamps the ring K to the frame at three places and its movement in the other direction releases it.

To clamp the ring K to the slave ring J a lever Kl. is pivoted at KBI on a part of the ring K. The short end of the lever, which is provided with a clamping friction pad, is urged against the ring J by a Spring K52. A handle K64 is fixed t 8} pin journaled in a bracket on a part of the ring K. Also fixed to the pin is a cam K65. The operator. by turning the handle K64, can clamp the ring K to the ring J, or can release ring K from ring J.

An eye tube R, Fig. 5, is mounted to slide on the parts KI and K2 0! the ring K. A vertical tube Rl, Fig. 10, is screwed into a base R6 provided with lugs having holes through which pass the rods Kll, Fig. 5, fastened in ears on the parts KI and K2, so that the eye tube R may he slid radially on the ring K. At the top of the cylinder R is a gimbal R3 for so holding the top of the tube R that its lower end is capable of universal motion substantially in a horizontal plane. Mounted on the tube RI, Fig. 10, is a ring R1 which may be turned by hand. The inside of this ring has an eccentric hole. Between the edge of the hole and a collar R! on the tube R is a ball RI I. By turning the ring R! the bottom of the tube may be adjusted crosswise against the stress of a spring RB. Another similar ring R8 with a ball, etc., is disposed at right angles, so that by turning the ring R8 the lower end of the tube R may be adjusted at right angles to the other adjustment. By turning both rings the lower end of the tube may be universally adjusted substantlally in a plane.

The tube R contains a glass RIO having marked on its upper surface, which is ground, a small circle or reticle RI I, Fig. 12. Glass RID is covered by a plain glass. The tube also contains lenses R" which reflect the real image of the object in focus on the ground surface of the glass RII. The universal adjustment of the lower end of the tube R so positions it that the image of the object may be brought into coincidence with the reticle. At the top of the tube R there is a magnii'ying lens R20, Fig. 10. Provision is made for artificially lighting the object by means of a small incandescent bulb to which current is supplied through the wire from an ordinary flashlight battery as shown in Figs. 4 and 5.

Preparatory to operation, the instrument is in zero position, Fig. 4, with the pointer S reading 0 on the scale onringJ.

The declination d and the local hour angle t of the celestial body are determined in the usual manner and likewise the dead reckoning, or assumed, latitude l of the observer.

The general mode of operation is as follows: The first procedure is to locate the point G,

' Fig. 1, which represents the projection on the observers meridian plane of the ground point of the For this purpose the wheel A, after being unlocked by the operation of the rod C35, is turned clockwise through an angle equal to the declination d (not to exceed 80") of the celestial body by the operation of the crank All, Fig. 14.

Thereby the pin AI, Fig. 4, moves the bar M downward against the pull of its spring to a position in which the engraved indicative line Ml over the axis of the pin assumes the position M2 in Fig. 1. The bar M is then clamped in that position by operating the rod Ml.

Inasmuch as the quadrant C is free from wheel A, it is held in its zero position, Fig. 6, by its spring C2 against the stop F3. But the pin All on wheel A is moved clockwise in the slot C and, inasmuch as the segment B is geared at BI, CI to the quadrant, the movement of the wheel A turns the segment anticlockwise about All! to move the pin B2 in a straight line towards 0 to a position in which its axis is at B2I, Fig.1, where the distance from 0 to B2I is equal to cos d.

The quadrant C is then clamped to the wheel A by operating the rod CI2. The wheel A and the quadrant are rotated anticlockwise by the crank All through an angle which, from the line Q, QI is equal to the local hour angle t, Fig. 1.

In this movement the segment B is moved bodily in unison with wheel A anticlockwise so that the axis of its pin B2 is moved on a radius equal to cos d from the point B2I to the point B22, and the bar P, moved by the pin B2 in its slot P2, is brought to the position in which its indicative line is the line P3 of Fig. 1.

The intersection of the indicative lines of the bar M and P fixes the point G, Fig. 1, which is the projection on the observers meridian plane of the ground point of the celestial body.

The eye tube R on the ring K is brought to a position in which the image of the engraved indicative line M0 on the bar M is seen as passing through the center of the reticle RH, Fig. 12, and the engraved line P4 on the bar P is seen as tangent'to the left side of the reticle and the indicative line of bar P passes through the center of the reticle. This is done by turning the ring K, moving the tube R radially on the rods K30 and adjusting the lower end of the tube by rings R1 and R8.

The ring K is then clamped to ring J by the operation of the handle K64 and thereby to wheel A, Fig. 4.

The next procedure is to locate the point E. Figs. 1 and 2, or the point El, Fig. 3.

In the case in which the declination d of the celestial body and the latitude l of the observer are of the same name, the wheel A is turned anticlockwise by the crank All through an angle equal to the co-latitude (l) of the observer,'

rotating with it the ring K carrying the eye tube R to the point E of Figs. 2 and 3.

The ring K is clamped to the frame F by operating the handle K52 and is unclamped from the ring J (and the wheel A) by operating the handle K64.

The quadrant C is unclamped from the wheel A by operating the rod CI2, Fig. 6, and is returned to zero position against the stop F3 by the spring C2. The wheel A is returned to zero position by the crank All, thereby returning the segment B and the bar P to zero position. The bar M is released by operating the rod M4 and is moved to zero position by its spring. Thereby all the parts are restored to zero position, except the ring K and the eye tube R carried thereby.

The next procedure is to measure the altitude h of the celestial body. For this purpose the wheel A is rotated clockwise by the crank All until the engraved indicative line M0 on the bar M, held by its spring against thepin A9, is seen through the eye tube R as passing through the center of the reticle RI I. This brings that line to the positionMIinFlg.2. Thedegreesandminutes,

throughwhichthewheelAisthusrotatedJsthe altitudehoftheeelestialbody,asshowninFig. 2.

The turning of the wheel A clockwise in this operation, while the quadrant C is held in zero position by the spring C2, rotates the segment B anticlockwise about its center pin A40, Fig. 6, and moves pin B2 in a straight line toward II to a position, Fig. 2, where the distance 0, B23, the axis of the pin,isequal tocosh. v

The next procedure is to measure the azimuth z of the celestial body.

The quadrant C is clamped to wheel A by operating rod C12, Fig. 6.

The wheel A is turned anticlockwise by the crank All and with it the quadrant C and the segment 13 until the axis of the pin B2 is brought to the position, B24, Fig. 2, in which the engraved line Pl on bar P is tangent to the left side of the reticle as seen through the eye tube B. This brings the indicative line of the bar into the position P6 in Fig. 2. The angle traversed from zero by the wheel A is equal to 180 minus the azimuth 2, i. e., 2 equals 180 minus that angle.

In the case in which the declination of the celestial body, d, and the latitude l of the observer are of opposite names, the eye tube R is located with reference to the point G as above described. The ring K is released from the frame and is clamped to wheel A (through ring J). It is rotated anticlockwise through an angle equal to 90+l, thereby bringing the eye tube to the point El, Fig. 3. As before, the ring K is then clamped to the frame and released from wheel A and the other partsare restored to their zero position.

The same procedure, as before, is then followed to move the bar M by turning the wheel A to such position that its engraved indicative line M isthe line M passing through the point El in Fig. 3, thereby determining the angle h, the altitude of the celestial body.

Then the same procedure, as before, is followed to move the bar P to such position that its engraved line P4 is tangent to the left side of the reticle, Fig. 12 and its indicative line is the line P6 in Fig. 3, thereby determining the angle 2, Fig. 3, which is the azimuth of the celestial body measured from the elevated pole.

I have provided counter mechanism and means to operate it, shown in Figs. 1326, by which the instrument may be operated by turning six knobs Y, D, T, L, H and Z, by moving a knob N, by turning the crank All, Fig. 13, and by operating the levers K52 and K54, Fig. 4. -At the end of an operation the given data, the declination d and the local hour angle t of the celestial body and the latitude Z of the observer are shown on the counters respectively DB, T0 and L0, Fig. 13, and the resulting data, the altitude h and the azimuth z of the celestial body, are shown on the counters HI and Z0. Thus the operator has before him on the counters all the data involved in an operation of the instrument.

The counter mechanism is controlled in part by six knobs Y, D, T, L, H and Z, Fig. 13, which are provided with handles by which they may be turned separately by the operator. Each knob, for example knob Y, is provided with a circular plate, such as Yl, which has on its periphery one or two arcuate recesses such as YZO. As shown in Fig. 13, all the knobs, except Y, are locked; D is locked by the periphery of Y being in the recess on the left of D; T is locked by the periphery of D being in the recess on the left of T; L is locked by the periphery of T being in the recess at the top of L; H is locked by the periphery of L' being in the recess at the right of H; and Z is locked by the periphery of H being in the recess on the right of Z. The arrangement is such that a quarter clockwise turn of a knob, beginning with Y, releases the next lmob so that all the knobs may be turned in succession but none can be turned out of its proper sequence. After all the knobs have been turned clockwise they may be turned anticlockwise to their starting positions in reverse succession beginning with Z. a

The turning of a'knob, for example knob Y, clockwise turns a gear, such as Y34, fast on a shaft Y2, Fig. 22, (All the knobs are of the same construction in this respect.) A ratchet on the bottom of the knob engages a ratchet Y fast on the shaft. A cap nut Y38 is screwed down on the upper end of shaft Y2 and compresses a spring Y39 against an annular shoulder on the knob to cause the ratchets to engage when the knob is turned clockwise, but permits the ratchet on the knob to slip over the ratchet on the shaft when the knob is turned anticlockwise, so that the shaft and the gear are not then turned. A pin Y lil, depending from the plate Yl, abuts against a stop YH on the frame when the knob is turned clockwise and against a. stop Y43 on the frame when the knob is turned anticlockwise, Fig. 23.

Let it be assumed that an operation of the instrument has been completed and the counters Z0, L0, DB and H0, Fig. 13, show the readings of the operations and that all the knobs Y, D, T, L, H and Z have been turned clockwisea. quarter turn.

, To prepare the instrument for a new operation, the operator turns all the knobs anticlockwise to the positions shown l3 and he turns the shafts L, T, D14 and HIE of the counters by their knurled ends so that the counters read zero. This is possible because all of these shafts are free from their clutches and are heldfrom rotation merely by friction, as will be described. Shaft Zl l only is still clutched, Fig. 16.

The operator turns knob Y clockwise a quarter turn.

The effects are:

(1) The shaft Z is unclutched.

(2) The quadrant C unclamped from the wheel A so that it is returned-to zero position by its spring, and

(3) The mechanism, which looks the wheel A, when in zero position, is released for action.

The turning of knob Y and shaft Y2 a quarter turn clockwise, Fig. 13, turns shaft Y3 a full turn anticlockwise, Fig. 14.

1) The eccentric Y4 on shaft Y3, Fig. 25, lifts the arm Z4 extending from an arm on the shaft Z6 to rock that shaft anticlockwise, Fig. 16. The rocking of shaft Z6 pulls the lever Z1, pivoted on an' arm on said shaft, to the left. This rocks the clutch yoke Z8, pivoted at Z9 on the frame, to the left and moves the clutch ZIU against the stress of the spring Z to disengage it from the clutch cone Zl2 which is fast to the gear Z15. This releases the shaft ZN, which is the azimuth countershaft, from the gear Z15.

The clutch, when drawn back, contacts with a friction stop ZIB which holds shaft Zl4 from ron the periphery of the hub Zll is a scale of sixty divisions representing the number of minutes through which the shaft is turned in one revolution. By mechanism, which is not shown as it is well known in this sort of counter, when the shaft Z and hub Z42 complete one revolution,

a recessed disc on the hub picks up the unit degree counter Z0l and causes it to advance onetenth of a revolution, and when the unit degree counter completes one revolution it Dicks up the tens degree counter Z0! and causes it to advance one-tenth of a revolution, and when the tens degree counter completes one revolution it picks up the hundred degree counter Z03 and causes it to advance one-tenth of a revolution. Counter wheels Z0l, Z0! and Z0! are loose on shaft Zll.

The hub Z00 is fast on shaft Z1. and at the completion of one revolution a recessed disc on the hub picks up the unit degree counter Z and causes it to advance one-tenth of a revolution. Similarly the tens degree counter Z06 and the hundred degree counter Z01 are advanced onetenth of a revolution. Counters Z05, Z06 and Z01 are loose on shaft Z.

The clutch devices on the other shafts Dll, Til, Lil and HI of the counters are the same as the clutch on Z14, except that th clutch device on L has two clutches one on the left and the other on the right, as will be described.

(2) when the knob Y and the shaft Y3 are turned, as above stated, cam Y20, fast on shaft- YI, Fig. 24, strikes the flange YZI on the left end of lever Y22, pivoted at Y" to the frame, to move down the right end of lever Y22. Projections on the right end of lever Y2! engage a collar C" on the rod Cl2 and move that rod down. Thi movement of rod Cl2, Fig. 6, pulls down the right end of lever Cll to release the pawl C21 from the ratchet C20, thereby releasing the lever C0 so that the left end of lever C4 on the quadrant C is lifted by the spring C8 l whereby the quadrant is released from the wheel A and is returned to zero by its spring C2, Fig. 5.

Rod Cl! is locked in its lower position by the slide C10, Fig. 24, which is impelled to the right by its spring C" so that the right end C12 of the slide enter the notch C14 in the rod CH.

(3) The cam Y20, Fig. 24, also strikes the iiange Y30 on the slide Y3l to move the slide to the left, against the tension of a spring Y32, to disengage its right end from the notch A55 in the rod A35. Then, when the operator turns the crank All, Fig. 13, to return wheel A to zero position, the spring A33, Fig. 6, pulls the lever A to the left and the pin A12 locks the worm shaft AB and the wheel A.

The instrument is now ready for a new operation.

According to whether the latitude of the observer and the declination of the celestial body are of the same name or of opposite names, the operator moves the knob N to the left or to the right, Fig. 17, as will now be described.

It is convenient to set the knob N, before the instrument is operated, to provide either for the condition (1) when the latitude l of the observer and the declination d of the celestial body are of resentin 180, and to cover the three lower figures on the azimuth counter.

The movement of the knob N and the shutter Ni to the left moves the member NI to the left, Fig. 17, so that its depending arm N4 is moved away from the stop L" on the clutch lever LI! and thereby will permit the clutch LIB to be moved to the left to engage the clutch cone secured to the gear L30 in the operation of the instrument to be described. And the depending arm N0 is moved against the stop L" on the clutch lever L03 and thereby prevents the clutch.

Lil from being moved to the right and from engaging the clutch cone Ll! on gear LI 5. The latitude counter L0, Fig. 13, is or has been set to 00 by the operators turning the shaft L by its knurled end, Fig. 17.

If the condition is (2) that the latitude of the observer and the declination of the celestial body are of opposite names, the knob N is moved down, as shown in Fig. 13, or to the right as shown in Fig. 17. Thereby the shutter NI is moved down, Fig. 13, to cover the upper set of figures on the azimuth counter Z0 and to expose the lower set of figures which then read 000.

The movement of the knob N to the right moves the member N3 to the right, as shown in Fig. 1'7. The arm N4 then is against the stop L and prevents the movement of clutch LIB to the left and the arm N5 is moved away from the stop L and permits the engagement of clutch L" with the clutch cone Ll! on gear MS, as will be described. The operator turns or has turned the shaft Lll so that the latitude counter L0, Fig. 13, reads 00.

The next step is to prepare the instrument to (4) To unlock the worm shaft A8 so that the.

wheelA may be turned by the crank.

(1) The cam DJ on shaft D3, Fig. 25, strikes the right end of lever D6, pivoted to the frame at D51, and rocks that lever clockwise. This removes the end D52 of that lever from beneath the projection D54 on lever D56, pivoted at DI. and permits the left end of lever D56 to be moved down, as shown in F g. 25. This permits the arm D on shaft D6 to move downward and the shaft D6 to rock clockwise, Fig. 20, under the the same name, or for the condition (2) when they are of opposite names.

Assume that condition (1) exists. The knob N, shown down in Fig. 13, is moved up in that figure,

.20 which are marked respectively 1, 8 and 0,.rep-

stress of the clutch spring (not shown but similar to the spring Zll, Fig. 16) and to allow the clutch lever D0, pivoted at D! on the frame, to move to the right and to cause the clutch Dll to engage the clutch cone D12 on the gear Dll. The gear DIS, Fig. 14, is one of a chain of meshing gearsLli, Tl5,Di5, andHli, the last meshing with the gear Ail, moimted on a stub shaft A02, to which gear the crank All is fastened.

when the crank and gearing are turned, the gear Lli, meshing with the gear A, fast on worm shaft A8, Fig. 17, turns the wheel A.

(2) Also, when the lever D6 is rocked, as above described, its shoulder D55, Fig. 25, is withdrawn from beneath th projection Hll on the end of the arm HI secured to an arm projecting from the shaft H8, thereby permitting the shaft Hi to be rocked clockwise, Fig. 21, under the stress of the clutch spring (not shown) to move the clutch K" into engagement with the clutch cone Hi2 on the gear Hi5. 1

(3) The cam D1, Fig. 24', on the shaft D3 strikes the arm C15 of slide C to move it to the left and withdraw its end 012 from the notch C" in the rod CI 2, so that the rod is brought to neutral position by the spring Cll, Fig. 6. I

(4) The cam D1, Fig. 24, also lifts the rod A35 to withdraw the pin A22, Fig. 6, from engagement with the collar A20 on the worm shaft A6, so that that shaft is unlocked and it and the wheel A may be turned by the crank.

The operator turns the crank to turn the wheel A clockwise and to rotate the declination counter shaft DIG until the degrees and minutes of the declination 11 appear in the openings over the declination counter Lt, Fig. 13. Thereby the pin A9, on the wheel A, Fig. 4:, moves the bar M downward to position M2, Fig. Ii.

While the turning of the crank also rotates the altitude shaft Hit, no account of this is taken until a later stage in the operation of the instrument, as will appear.

The next step is to prepare the instrument to show the local hour angle t, Fig. 2, on the counter re, Fig. 13. I I

The operator turns the knob T a quarter turn .clockwise, thereby turning the shaft T2 with it and turning the shaft T3 anticlockwise a half turn, Fig. 1e.

The efiects'are:

(1) To unclutch the declination shaft Didi.

(2) To engage the clutch on the local hour angle shaft TM.

(3) To clamp the bar M in position M2, and

(4) To clamp the quadrant C wheel at.

(1) Cam T5 on shaft T3, Fig. 25, depresses the right end of lever D58, and thereby its left end is raised to lift the lever D5 and rock the shaft D6 anticlockwise, Fig. 20, to disengage the clutch Dill from the gear M5. The shaft Did, to which the clutch is splined, is held from rotation, on positively turned, by a friction pad against which the clutch is pressed when moved; to the left.

(2) Cam ft, Fig. 25, also strikes lever Till. pivotedat its upper end to the frame, and moves it into the position shown in Fig. 25. The notch TH is thereby removed from above the melee tlon Tit on the lever Tdll pivoted to the dine at TM. Thereby the left end of lever We ceases to uphold arm Til on shaft T6 and that shaf 19 is rocked clockwise by the clutch sprhig. which causes the clutch Ti 0 to engage the clutch cone Tit on gear Tit.

(3) Cam TH on shaft T3, Fig. 25, strikes against the arm MM on the rod M40 to withdraw its beveled end from beneath the beveled end of the clutch rod M4 to permit the rod to be moved down by the spring M6, Fig. 8, thereby clamping the bar M with its engraved indicative line in position M2, Fig. 1.

(4) Cam T, Fig. 24, strikes against the flange Ylll on the right end of lever Y2; to raise it and the rod CIZ. Raising the rod. on, Fig. t, moves down the left end of lever (255i and clamps the lever C4, pivoted on the quadrant C, to the wheel A, so that, when the wheel A is turned the quadrant C will turn with it. After the rod Cl2 has been raised, as just above described, the cam Tli, Fig. 24, passes out of engagement with the flange Ylll and the spring C, Fig. 6, returns the rod Cl2 to neutral position.

The operator turns the crank, Fig. 14, to rotate the wheel A and quadrant C anticlockwise thereby rotating the shaft TH until the counter T0, Fig. 13, shows the degrees and minutes of the local hour angle t. In this operation on the segment B. Fig. 6 is carried bodily anticlockwise about the center 0 to move the pin B2 so that its axis is carried from position B2! to 32$, Fig. and thereby the bar P is moved to the right to bring its indicative line into position Pt. 1

The operator by turning the ring R; and morning and adjusting the eye tube R brings the eye tube into the position, shown in Fig. 12, in which the engraved indicative line Mil on the bar ltd passes through the center of the reticie Hi i, 12, and the engraved line P4 on the bar 1? is ten gent to the left side of the reticle and the indicative line of the bar passes through the center of the reticle. Thereby the eye tube is brought over the point G, Fig. l, which is the point of intersection of the indicative line of bars and P.

The operator next turns lever Fig. to clamp ring K to the slave ring J and also to wheel A, as ring J and wheel A are connected together by the post J5, Fig. 5.

Eli

Inasmuch as the next operation of the metrement is to move the eye tube from the Fig. l, to the point E in case the declination of the observed celestial body and. the latlimde the observer are of the same name, Figs. '5. and 2, or to the point El, Fig. 3, it they are or opposite names. the operator moves the'lrnoh N either the right, Fig. 17, or to the left, and

latitude counter Lil to read 00 unless he has el v ready done so. as above described.

The next step is to prepare the instrument so that the latitude counter Fig. 12, will its cate the degrees and minutes through which the wheel A is turned to bring the eye tube to I point, E, Figs. 1 and 2, or to the point The operator turns knob L, l3, and its t a quarter turn clockwise, thereby turning shaft Fig. it, a toll. turn antic wise.

lhe effects are:

(1) To uncliiteh the shaft "if l 3.

(2) To engage the appropriate clutch on shaft L36.

(3) To release the bar ML,

Us) To nnclamp quadrant; G from w (1) (Jam we, on shaft L8, Fig. 25, meter, lawn the right end or lever This raises the left end of. lever TN to lift arm T6 on "lit rock the shaft anticlockwise, Fig. 19, to gage the clutch Till from the cluteh cone and gear "rat. The clutch and the shaft held by the friction 119. The projection I'll; on lever Tm, Fig. 25, is engaged by the noteh in the lower end of lever Ti 3. which is pulled a T22 to the right, to hold down the right end of. lever TZtl.

(2) 6am L20 also moves down the right end at lever Lil, pivoted to the frame at L22, to withdraw its upper end L23 from the flange on lever L24, pivoted to the frame at Dbl. This permits the left end of lever L25 and the arm L6 to fall and the shaft L8 to turn clockwise, Figs. 17 and 18, under the stress of one of the clutch springs (not shown) on shaft L16.

(3) Cam LI, Fig. 25, strikes against and lifts arm M4! on rod M to push its beveled end un der the beveled end of rod M4 to raise Ml, Fig. 9,

' and thereby release the bar M.

(4) Cam L", Fig. 24, strikes against and moves down the arm C80 and the rod CII. This moves down the lever C", Fig. 6, so that when the tail of the pawl C21 strikes lever C", as it will when the quadrant C is turned anticlockwise in the next operation of wheel A and the quadrant, the pawl will be released from the ratchet C20 and the spring CBI will release the clamping lever Cl from the wheel A, thereby disengaging the quadrant from the wheel. The rod CII, Fig. 24, is locked in its down position by the end C12 of slide entering the notch CH, due to the pull of the spring C! i,

In the case in which the declination of the celestial body and the latitude of the observer are of the same name, the knob N, Fig. 17, has been moved to the left and the latitude counter shaft LO has been set to read 00, as above described. In such case the left clutch spring (not shown) on the shaft Lil moves the left clutch Ll. into engagement with the clutch cone L18 on gear L". The spring rocks the lever L32, pivoted to the frame at L, to the left and also lever L38, pivoted at L", to the left. The hub of lever LIB has an arm L38 provided with a slot into which extends a projection L" on lever III also pivoted at L.

Lever L42 has teeth on its segmental end which engage with the teeth on a segment LS2 fast on shaft Li. By these means the clutching action of the left spring rocks the shaft LI clockwise.

Lever L38 has teeth on its segmental end which engage the teeth on the segmental end of lever LII, pivoted on the frame at L35, and when the toothed end of lever L39 rises, its arm L31 ls rocked to the right. But this has no effect on the clutch arms L38 which are held from movement to the right by the projection N! on member NI.

The gear L30 meshes with a gear L80 Journaled on a stub shaft Lil secured to the frame, and the gear LI. meshes with a gear A", Fig. 15, fast on shaft Al. Thus the shaft LII may be turned by the operator's turning the crank All to indicate the anticlockwise rotation of the wheel A 90-l (1 being the latitude of the observer), when the declination and the latitude are of the same name, Fig. 1.

The operator turns wheel A by the crank All, Fig. 14, and with it the ring K anticlockwise until the latitude counter Ll reads the latitude 'l of the observer. This turns the wheel A through the angle 90l, because the counter wheel LII, Fig. 17, loose on the shaft Lil, has nine digits, 0 to 8 (instead of the usual ten on such a wheel) and turns reversely, i. e., from 0 to 8 to 7, etc., in thisoperation.

The rotation of the ring K brings the eye tube It to the position E, Fig. 1.

L4 on shaft L8, thereby turning that shaft anticlockwise, Fig. 17, and disengaging the clutch LII from the gear Llll and releasing shaft LII.

The operator cranks the wheel A clockwise until the pin A9, Fig. 4, moves the bar M down so that its engraved indicative line MO passes through the center of the retlcle, Fig. 12, as seen through the eye tube at E, Fig. 1, thereby bringing that line on the bar into position M5, The altitude h, in degrees and minutes, will appear on the altitude counter HI, Fig. 13. It may be noted that the shaft H, which carries the altitude counter, has been clutched to the gear HI! and rotated by the crank since the knob D was turned.

The next step is to prepare the instrument to indicate the azimuth a on the azimuth counter ZlLFig. 13.

The operator turns the knob Z, Fig. 13, and likewise the shaft Z2, Flg.-14, a quarter turn clockwise, thereby turning the shaft 23 anticlockwise a half turn.

The effects are:

(1) To unclutch the shaft Hi l.

(2) To engage the clutch on shaft Z.

(3) To restore lever C" to neutral, and

(4) To clamp the quadrant C to wheel A.

(1) Cam Z20 on shaft Z3, Fig. 25, lifts the arm H4 on an arm on shaft Hi to rock that shaft anticlockwise, Fig. 21. This disengages clutch Hll to release the shaft H l 4, which through the clutch and the friction pad III! is held frictionally from rotation. Arm H4 is held in raised position by the shoulder D on lever D5, Fig. 25, engaging the flange Hli on arm H4, lever D5 being pulled anticlockwise by the spring D31, one end of which is fast to the lever D5 and the other end is fast to the lower end of lever ZZI, pivoted at Z21 to the frame,

(2) Cam Z20 also rocks lever Z2i clockwise to withdraw the notch Z2 at its upper end from beneath the flange on the end of arm Z4 which arm projects from an arm on the shaft Z6. Thereupon the shaft Z6, Fig. 16, is turned clockwise by the clutch spring Z! I, which causes the clutch Zll to en age the clutch cone Zi! on gear Zii.

(3) Cam ZII on shaft Z3, Fig. 24, strikes a depending arm C13 on the left end of slide C1! and moves the slide to the left to withdraw its right end C12 from the notch C14 in rod CII. Thereupon spring C, Fig. 6, restores the lever CI! to neutral position.

(4) Cam Zlll on shaft Zi, Fig. 24. lifts the end of lever C90, pivoted-at D3, to turn the segmental gear C on its right end clockwise, thereby turning the pinion C82, fast on the lever Y", to raise the right end of that lever and the rod CH. The

The operator turns lever Kn. Fig. 4. to clamp ring K to the frame and turns lever K to release ring K from slave ring J and wheel A.

The next step is to prepare the instrument-to indicate the altitude h on the altitude counter HO, Fig. 13.

The operator turns the knob H a quarter turn clockwise and likewise the shaft HI, thereby tuming the shaft HI, Fig. 14, a full turn anticlockwise.

' The effect is:

.(1) To unclutch shaft'Lll.

(1) Cam K, Fig. 25, moves down the right end of lever L to raise its left end and the arm raising of rod Cil, Fig. 6, moves down the left end of lever Cil, thereby depressing the arm Cl and the clamp Cl'to clamp the quadrant C to the wheelA. The rod Cl! isreturned to neutral position by the spring C.

It will be noted that the upper openings show the azimuth counter ZI, Fig. l3,reading 180", the

I shutter NI being in its upper position to expose the upper counters and cover the lower counters.

The operator turns the crank to rotate to wheel A and quadrant C anticlockwise, thereby carrying the segment B bodily anticlockwise about the center 0, Fig, 6. This moves the pin B2 on B anticlockwise and its axis from position B" to position 1324, Fig. 2, and the pin 13!, being in the slot P2 of the .bar P, Fig. '1, moves the bar P to the right until its engraved line P4 is tangent to the left side of the reticle RI I when seen through the eye tube R and the indicative line of the bar P is in position P6, Fig. 2. The reading on the upper azimuth counter Z0, Fig. 13, is the azimuth e of the celestial body measured from the elevated pole.

This completes the operation of the instrument with the declination, the local hour angle, the altitude and the azimuth of the observed celestial body and the latitude of the observer shown on their respective counters in the case when the declination of the body and the latitude of the observer are of the same name.

In case the latitude of the observer and the declination of the celestial body are of opposite names, the knob N is set to the right, Fig. 17, or down in Fig. 13, and the shutter Nl exposes the lower figures on the azimuth counter shaft Z and covers the upper figures, Fig. 13. The member N3 is moved to the right, Fig. 17. The operator sets or has set the latitude counter to 00. These settings should be made at any time before the operation of knob L.

Then, when the knob L is turned, the shaft L8 is rocked clockwise and the right end clutch L", Fig. 17, is clutched to the clutch cone on gear LI 5. The arm N4, being in contact with the stop L, prevents the left clutch Llli from engaging the clutch cone Ll8.

The ensuing procedure is the same as before; the wheel A and the ring K clamped to it, are rotated anticlockwise to bring the eye tube R to the point El, Fig. 3, by turning the latitude shaft LN, then geared to wheel A, until the latitude counter-L0 reads the degrees and minutes of the latitude of the observer for the second time. The ring K is clamped to the frame and unclamped from the slave ring J and wheel A. The lmob H is turned. The wheel A is rotated until the engraved indicative line on the bar M passes through the center of the reticle as seen through the eye tube, i. e., line M5 of Fig. 3. The altitude counter H0 then shows the altitude of the celestial body.

The knob Z is then operated and the operator turns the wheel A and with it the segment B and the azimuth counter Z0, then geared to wheel A, until the engraved line on the bar P is tangent to the left side of the reticle as seen through the eye tube and the indicative line of bar P passes through the center of the reticle. This moves the axis of the pin B from position B to position B28 and the indicative line of the bar is line P6 of Fig. 3. The counter Z0 shows the azimuth z ures marked, preferably in black, clockwise from 0 to 55.

Counter Hlfl, loose on shaft Hl40, has an upper set of figures marked, preferably in red, anticlockwise from 0 to 9 and a lower set. of figures marked, preferably in black, clockwise from 0 to 9. When the wheel A, Fig. 6, is rotated clockwise one degree, i. e., 5 of its circumference, the shaft Hl40 and the counter Hill make one revo lution anticlockwise. When the counter Hlll has made one revolution it causes the counter Hl42 to make of a revolution in the same direction, thereby indicating one degree. Thus the counters Hill and HM! respectively indicate the rotation of the shaftHllll in minutes and degrees.

At the start of an operation of the instrument the shaft Hl40, which is unclutched from the driving gear HIS, is turned by the operator so that its counters read the observed altitude in degrees and minutes.

The shaft Hl40 is clutched to the driving gear HI 5 when the operator turns the knob D, Fig. 15,

a quarter turn clockwise. The shaft continues to turn, either one way or the other as before described, until after the knob His given a quarter turn by the operator and the wheel A is then observed altitude and the computed altitude.

of the celestial body as measured from the ele- I v'ated pole.

In case the latitude of the observer is south, the true azimuth measured from the elevated pole may .be read by shifting the knob N and the shutter NI up to expose the upper set of figures on Z0, Fig. 13.

This completes the operation and the instrument can be prepared for another operation in the manner already described.

A modification shown in Figs. 28-32 enables a.

the same as'the shaft H, shown in Fig. 21, ex-,

cept that the shaft HMO is provided with two counters Hill and EH2.

Counter Hill, fast on shaft HMO, has two sets of figures, an upper set marked, preferably in red, anticlockwise from 0 to 55 and a lower set of 118- There will be two readings on each counter, one given by the upper or red figures and one by the lower or black figures.

As .the intercept will in practice never be more than 4, the reading is taken which is the lesser of the two. If that reading is the upper orred figures the intercept is away, and if it is the lower or black figures it is towards by the number of de rees and minutes shown on the counters. If the counters read zero the computedaltitude is the same as the observed altitude.

The instrument shown in Figs. 4-12 may be employed to carry out the method illustrated in Figs. 1-3. without the use of the counter mechanism shown in Figs. 13-26. In' such case there is no record of the data, either given or resulting, shown by the instrument.

In such case, Fig. 27, the worm shaft A6 is extended beyond the frame F and is provided with a crank AIG and with a counter All; to indicate the number of whole turns and V60 parts of a turn of .the shaft A6 to indicate the number of degrees and minutes which the wheel A will have been turned. The rod A35 extends merely a short distance beyond the frame and may be provided with a knob for the convenience of the operator. The rod Ml likewise extends but a short distance beyond the frame and may be 'lifted by a lever M0 pivoted in a bracket on the server, having in combination a supporting frame,

an indicator wheel having worm teeth on its periphery and a pin projecting from the surface of said wheel adjacent to its periphery, a worm shaft engaging the worm teeth on said wheel, means for locking the indicator wheel in its zero position, a bar extending lengthwise across the wheel and mounted in'guides so as to be capable of bodily movement at right angles to its length, means for pressing said bar against the pin on the wheel, means on said bar to indicate visibly a line parallel with said bar and passing through the axis of said pin, a clamp to clamp the bar to the frame, means to operate said clamp, a quadrant mounted concentrically with the indicator wheel and having internal gear teeth on its periphery, a clamp to clamp the quadrant to the wheel, means to operate the clamp, a spring to return the quadrant to zero position, a'segment pivoted on said wheel at a distance from the center of said wheel equal to one-half the distance from the center of the wheel to the axis of the pin projecting therefrom, gear teeth on the periphery of the segment meshing with the internal gear teeth on the said quadrant, the pitch line common to said meshing gear teeth being at a distance from the center oi! said wheel equal to the distance from the center of said wheel to the axis of said projecting pin, a pin projecting from said segment and having its axis coincident with the common pitch line of said meshing teeth when said segment is in zero position, a second bar having its length at right angles to the length of the first-named bar and'mounted in guides so as to be capable of bodily movement perpendicular to its length and having means to indicate visibly a line parallel to said bar and in a predetermined relation to a parallel line passing through the axis of said pin on said segment, said bar having a slot in its bottom surface into which said pin projects, a slave ring concentric with said indicator wheel and rigidly connected thereto, an eye tube carrying ring mounted concentrically with said wheel and capable of being turned about its center, a clamp to clamp said ring to the frame, means to operate the clamp, a clamp to clamp said ring to the slave ring and the wheel, means to operate said clamp, an eye tube mounted on a carriage slidable radially on said eye tube carrying ring and having a uni, versal adjustment for its lower end, said eye tube containing a reticle adapted to be associated with the images of said visible means. on said 'movablebars, and a series of counters operated by the worm shaft to indicate the number oi! degrees and minutes through which said wheel may be turned by the rotation of said worm shaft.

2. An apparatus for indicating the altitude of a celestial body and the azimuth of the body, when there are given the declination and the local hour angle of the celestial body and an assumed or dead reckoning latitude of the observer, having in combination a supporting frame, an indicator wheel, a shaft to rotate said wheel, a pin projecting from the surface of said wheel adjacent to its periphery, a bar extending lengthwise across the wheel and mounted in guides so as to be capable of bodily movement at right angles to its length and adapted to be moved by said pin, means on said bar to indicate visibly a line parallel with its length and passing through the axis of said pin, a clamp to clamp the bar to the frame, means to operate said clamp, a quadrant mounted to turn about the same center as the indicator wheel and having gear teeth on its periphery, a clamp to clamp the quadrant to the wheel, means to operate the clamp. a segment pivoted on said wheel at a distance from the center of said wheel equal to one-half the distance from the center of the wheel to the axis of the pin projecting therefrom, gear teeth on the periphery of the segment meshing with the gear teeth on said quadrant, the pitch line common to said meshing gear teeth being at a distance from the center of said wheel equal to the distance from the center of said wheel to the axis of said projecting pin, a pin projecting from said segment and having its axis coincident with the common pitch line of said meshing teeth, a

second bar having its length at right angles to the length of the first-named bar and mounted in guides so as to be capable of bodily movement perpendicular to its length and adapted to be moved by said pin on said segment, means on said bar to indicate visibly a line parallel to its length and having a predetermined relation to a parallel line passing through the axis of said pin on said segment, a ring mounted concentrically with said wheel and capable of being turned about its center, a clamp to clamp said ring to the frame, means to operate the same, a clamp to clamp said ring to the wheel, means to operate the same, an eye tube mounted on a carriage slidable radially on said ring and having a universal adjustment for its lower end, said eye tube containing a reticle adapted to be associated with the images of said visible means on said movable bars, and counters operated by said wheel-rotating shaft to indicate the number of degrees and minutes through which said wheel may be turned.

3. An apparatus for indicating the altitude of a celestial body and the azimuth of the body, when there are given the declination and the local hour angle of the celestial body and an assumed or dead reckoning latitude of the observer, having in combination a supporting frame, an indicator wheel having worm teeth on its periphery and a pin projecting from the surface of said wheel at a given distance from the center thereof, a worm shaft having a worm engaging with the worm teeth of the wheel, means for locking the indicator wheel in its zero position, a bar extending across the wheel and mounted in slides so as to be capable of bodily movement at right angles to its length, means for pressing said bar against the pin on the wheel, means on said bar to indicate visibly a line parallel with said bar and passing through the axis of said pin, a clamp to clamp the bar to the frame, a'quadrant mounted to turn about the same center as the indicator wheel and having internal gear teeth on its periphery, a clamp to clamp the quadrant to the wheel, a spring to return the quadrant to zero position, a segment pivoted on said wheel at a distance from the center of said wheel equal to one-half the distance from "the center of the wheel to the axis of said pin, gear teeth on the periphery of said segment meshing with the internal gear teeth on the said quadrant, the pitch line common to said meshing gear teeth being at a distance from the center of said wheel equal to the distance from the center of said wheel to the axis of said projecting pin, a pin projecting from the segment and having its axis coincident with the common pitch line or said meshing teeth, a second bar having its length at right angles to the length of the first-named bar and being bodily movable on guides perpendicular to its length and having visible means lengthwise of the bar 7 

